I think its ridiculous the nhs don't test to be honest, I'm a carrier of GBS and the hospital found out after my first miscarriage,( i've had 3) but no one bothered to tell me, I found out by chance when i was pg with my 3rd son and after 2 miscarriages. I was fuming to say the least! Now i know i'm a carrier I have to pay for my own test at 37 weeks. £32 a small price to pay for peace of mind tho.
I lived in Germany for 4 years and they test every pregnant women for it there which i strongly believe they should do here too!
If you are really concerned check out thos website it tells you everything you need to know about GBS
www.gbss.org.uk